It is standard in the semiconductor industry to use a wafer cassette to hold a lot of (usually 25) wafers. Many of the tools for the various semiconductor processor activities, such as implantation, photo resist, and testing, use the same apparatus having a transfer blade designed to insert and retrieve wafers from a standard cassette. The transfer blade of such apparatus requires mechanical alignment with the wafer shelves of the cassette. It is known in the arts to align the top wafer shelf in the cassette, the bottom wafer shelf in the cassette, e.g., the 25th wafer, and a wafer selected from somewhere near the middle. These three alignment points are generally sufficient to ensure that the remainder of the wafer shelves are suitably aligned with the transfer blade. Adjustments are made through an operator interface generally requiring the use of the operator's hands. Typically, the operator peers into the wafer cassette and performs the alignment by observing the position of the transfer blade mechanism relative to the wafer shelves of a cassette, making mechanical adjustments as required.
Problems arise in the art due to conditions hampering the visual observation. For example, it is generally dark within the wafer cassette. It is known for the operator to attempt to shine a flashlight into the cassette. This solution is successful to some degree, but does not provide ideal illumination due to obstructions. Additionally, this requires one of the operator's hands, which would otherwise be available for making mechanical adjustments. Additionally, because the wafers have a highly reflective surface, glare and reflected light make observation of crucial areas difficult. These and other complications in making visual observations in order to perform transfer blade alignment lead to additional problems such as increased time required to perform the alignment process, decreased yield due to improper alignment, and possibly damaged wafers.
It would be desirable in the arts to develop devices, systems and methods providing improved illumination for transfer blade alignment relative to a wafer cassette. Such improvements would provide many advantages, including reduced cycle time, increased yield, convenience, and more accurate alignment.